[Clubber]

The system would also need to detect which direction the traffic was going. In morning rush hour, outbound would be much heaver than inbound (of your neighborhood) so it would typically be unidirectional.

[nitrogen]

I've seen such lights in remote construction sites on road trips. They do exist.

[ghaff]

It’s not uncommon in the US West where you may have lengthy stretches of road that are single lane because of construction.